Disease Commonly Known as Scabies

¶ … disease commonly known as scabies is an itchy skin rash which is caused by the mite Sarcoptes scabiei. The scabies mite is a very small arthropod, which is about the size of a small grain of salt. This mite is actually a distant relative of the spider, although many people believe this rash is caused by bacteria. The mite is microscopic, but much larger than bacteria, having many cells instead of just one. Mites are parasitic animals, while bacteria and viruses are parasitic, they are not animals.

Bacterial infection may occur if the infested person scratches at the irritated area of skin, but this is a separate condition caused by breaking the skin. Approximately 300 million worldwide cases of scabies infestation occur every year.

Transmission of scabies occurs when a fertilized female mite transfers to the new host's skin. This mite will burrow into the horny layer of the skin at a rate of approximately two millimeters per day. The mite will deposit between two to three eggs per day into the skin for a period of ten days, and then the female mite will die. In order for the mite to transfer to a new host, there must be skin contact with an infected person or items such as clothing that may have come into contact with the infected skin recently. Scabies spreads most rapidly in crowded conditions with frequent skin-to-skin contact between people, such as hospitals, child-care facilities, and nursing homes. The skin contact usually must be prolonged for the infestation to spread, so while a handshake will not generally spread the mite, sexual partners or household members will easily contract scabies. It is possible for infestation to spread by sharing clothing, towels, or bedding, but it is less likely than direct skin contact. Pets, such as cats and dogs, may become infested with a different kind of scabies mite and develop a condition commonly known as mange. This mite can spread to people which have skin contact with the infested animal, however this mite dies within a few days and cannot reproduce in human skin. Contracting the scabies mite that infects animals can cause skin itching or irritation, but it does not have to be treated (in the human) and is not the same as human scabies, though repeat infestations of this related mite may occur in the human until the pet is treated.

The scabies mite is common in many areas of the world. The preferred areas of infestation include a person's hands and feet, especially the webbing between fingers and toes. The buttocks and genitals, especially the penis, are also commonly infested. The breast or shoulder-bade area is also prone to scabies infestation and irritation.

Warm areas of skin, such as those found under the waistband of pants or under watches or jewelry are particularly prone to infestation. The adult female mite normally lives for approximately ten days, but can actually live up to a month in the human body. Mites can be found in clothing and other items which have come into prolonged skin contact with a person's affected areas, but the mites will only survive up to seventy-two hours away from the human body.

The scabies mite causes an allergic reaction that is often worse at night due to the warmth of being in bed. Increased sensitivity may also be noted after a hot shower or bath, or during and after intense physical activity. The rash generally looks similar to pimples or burrows in the skin. The rash causes intense itching, and the itching may spread to the entire body even if the rash is only obvious in one area. In the case of sexually transmitted scabies, the lesions are often found only on the genitals, buttocks, thighs, and lower trunk area. Penile or scrotal infections may not always itch, and usually appear as inflamed lumps of a dark red or brown color that can be up to twelve millimeters in diameter. Scratching at the irritated skin often causes sores, which may become infected with bacteria. In incubation period from infestation to when symptoms will begin to appear is generally around four weeks, or up to six weeks, if the person has never been infected previously. People who have been infested with scabies before will have symptoms begin to appear much more rapidly, sometimes within a few hours of infestation. This is due to the increased sensitivity of the skin from previous infestations. People do not become immune to infestation after treatment.

Diagnosis of scabies is most commonly made by an observation of the irritated skin and locating a scabies-like rash or skin burrows. The burrows are often difficult to see themselves, as they are only between five to fifteen millimeters long and about the width of a thread. There may be a blister at the end of the burrow, but not always. Doctors may chose to take a skin scraping to look for mites, mite eggs, or mite fecal matter in the skin to confirm the diagnosis, but this method is also not perfect. Often, test results will be returned negative for scabies even if the person is in fact infested because there are usually less than ten mites on the entire body of an infested person.

In many cases, by the time an infested person seeks medical treatment, the burrows have been scratched due to itching, and the burrows have been disrupted. Often by this time there is also a secondary infection of bacteria. People who shower frequently may be more difficult to diagnose. Additionally, if topical steroids have been used previously it may make the clinical symptoms harder to diagnose.

The scabies rash may become increasingly worse if not treated, especially if bacterial infection has occurred. People who have weakened immune systems and the elderly may contract a more severe from of scabies known as Norwegian or crusted scabies. In extreme untreated cases, Norwegian scabies can be fatal.

Anyone who is diagnosed with scabies should be treated. Anyone who has prolonged skin contact or sexual contact with that person should also be treated. Treatment should be done at the same time to prevent reinfestation. Generally, a five percent permethrin cream is used for treatment. The cream should be applied to clean skin, and the patient should try to keep the skin cool. The cream should be applied in a thin layer to all areas of skin below the neck. Having another person apply the cream is often recommended so that no area of the skin is missed.